I recently used a bloom filter to achieve a log message anti-spam feature. In the logger I hashed the messages and inserted into the filter. If the entry was present I didn’t output the messages. Then every few seconds I would iterate over the filter and clear all the bits. It worked out nicely that I didn’t have to worry about atomically clearing all the bits in the filter, if messages were coming in and any of their bits had been cleared that was sufficient to cause them to be logged again. This was much more efficient than the previous implementation which kept a count of messages seen and would saturate at N and had the effect that if a particular message was being repeatedly logged it would be seen, just at most at the rate at which the filter was being cleared.
After being aware of bloom filters for a while it was quite satisfying to organically find a real use for one that was such an improvement.